The present application relates to bidirectional bipolar transistors which have separate base connection regions, as well as separate emitter/collector diffusions, on both surfaces of a monolithic semiconductor die.
Note that the points discussed below may reflect the hindsight gained from the disclosed inventions, and are not necessarily admitted to be prior art.
Bi-directional bipolar transistors or “B-TRANs” have been proposed for use as high voltage bi-directional switches, based on their low on-voltages at high current levels. Earlier patent applications of Ideal Power Inc., many of which are now issued, have described many features of B-TRAN devices and methods, including many options, improvements, and alternatives. For example, see U.S. Pat. Nos. 9,029,909, 9,190,894, 9,203,400, 9,203,401, and 9,209,713, all of which are hereby incorporated by reference; also see pending U.S. application Ser. No. 14/566,576, Ser. No. 14/599,191, Ser. No. 14/882,316, Ser. No. 14/918,440, Ser. No. 14/937,814, Ser. No. 14/992,971, Ser. No. 14/935,344, Ser. No. 15/018,844, Ser. No. 15/055,514, Ser. No. 15/083,217, and Ser. No. 15/083,230. All of these applications and patents, and all their direct and indirect priority applications, are hereby incorporated by reference.
The structure of an NPN B-TRAN device, in one example, is shown in FIG. 6. An enhancement to the B-TRAN structure of FIG. 6 is shown in FIG. 7. In this figure, the trench that was filled with dielectric in FIG. 26 has a trench which is lined with a dielectric (e.g. silicon dioxide), and is subsequently filled with conductive polycrystalline silicon. The polycrystalline silicon electrode located in each trench is in turn electrically connected to the n-type emitter diffusion region present on at least one side of the trench.